Microfluidic film and method for fabricating the microfluidic film

ABSTRACT

Provided is a microfluidic film including a base film, a microchannel, which is formed on the base film and through which a fluid flows, and a through passage, which is configured to pass through the base film and through which the base film stacked on an upper portion or a lower portion of the base film and the fluid communicate with each other.

CROSS-REFERENCE TO RELATED APPLICATION

This application claims the benefit of Korean Patent Application No.10-2021-0126355, filed on Sep. 24, 2021, in the Korean IntellectualProperty Office, the disclosure of which is incorporated herein in itsentirety by reference.

TECHNICAL FIELD

The present invention relates to a microfluidic film and a method offabricating the microfluidic film, and more particularly, to amicrofluidic film including a microchannel, a base film and a throughpassage for fluid communication with another base film stacked on orbelow the base film, and a method of fabricating the microfluidic film.

BACKGROUND ART

Various electronic components have been developed and integrated in atwo-dimensional space and developed as modern integrated circuit (IC)chips. By the way, when electronic circuits are constituted in atwo-dimensional (2D) plane, circuit configuration is complicated due tospace limitation. Currently, in order to solve this problem, logiccircuits are stacked not in a horizontal direction but in a verticaldirection. However, it is not easy to perform organic connection ofcircuits when configuring three-dimensional circuits stacked in thevertical direction compared to a case where circuit configuration isperformed in a 2D plane. For organic connection betweenthree-dimensional (3D) circuits, interest in through-silicon via (TSV)technology is increasing.

These points may be similarly applied to microfluidics. As a measure forsolving these problems, in microfluidics, a method of fabricatingthrough-holes based on silicon etching using photolithography may beintroduced. However, because extensive photomasks are required in aphotolithography process and complicated processes, such as exposure anddevelopment, are required, process cost is too high. Thus, in order tosolve this cost problem, a method of fabricating through-holes bycontinuously making molds having a desired structure by usingsoft-lithography may be introduced. However, because these molds aredisposable, cost reduction is possible, but mass production isdifficult.

DISCLOSURE OF THE INVENTION

The present invention provides a microfluidic film including amicrochannel, a base film and a through passage for fluid communicationwith another base film stacked on or below the base film, and a methodof fabricating the microfluidic film.

According to an aspect of the present invention, there is provided amicrofluidic film including a base film, a microchannel, which is formedon the base film and through which a fluid flows, and a through passage,which is configured to pass through the base film and through which thebase film stacked on an upper portion or a lower portion of the basefilm and the fluid communicate with each other.

According to another aspect of the present invention, there is provideda method of fabricating a microfluidic film, the method includingfabricating a basic mold, the basic mold including a base member, afirst base groove formed on the base member to extend in a longitudinaldirection and having a storage space therein, a second base grooveformed on the base member, being spaced apart from the first base grooveand having a storage space therein, and a third base groove formedbetween the first base groove and the second base groove so that thefirst base groove and the second base groove communicate with eachother, fabricating a master mold that is repeatedly usable by using thebasic mold as a template, and fabricating a microfluidic film by usingthe master mold as a template, the microfluidic film including amicrochannel through which a fluid flows and a through passage forcommunicating with the microfluidic film stacked on an upper portion ora lower portion of the microchannel.

A microfluidic film and a method of fabricating the microfluidic filmaccording to the present invention have the following effects.

First, because the microfluidic film includes a base film, amicrofluidic channel and a through passage for fluid communication withanother base film stacked on or below the base film, fluid movementbetween the stacked base films is possible.

Second, the microfluidic film including both the microfluidic channeland the through passage can be produced with low cost by using apre-fabricated master mold.

Third, because the master mold can be repeatedly used, a microfluidicmodule including the microfluidic channel and the through passage can bemass-produced.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a microfluidic film according to anembodiment of the present invention;

FIG. 2 is a block diagram illustrating a method of fabricating amicrofluidic film according to an embodiment of the present invention;

FIG. 3 is a schematic diagram illustrating a process of fabricating abasic mold that serves as a template for fabricating a master mold ofthe method of fabricating the microfluidic film shown in FIG. 2 ;

FIG. 4 is a schematic diagram illustrating a process of fabricating amaster mold of the method of fabricating the microfluidic film shown inFIG. 2 ;

FIG. 5 is a schematic diagram illustrating a state in which the mastermold fabricated according to FIG. 4 is separated from the basic mold;

FIG. 6 is a schematic diagram illustrating a method of fabricating amicrofluidic film by using the master mold of the method of fabricatingthe microfluidic film shown in FIG. 2 ;

FIG. 7 is a schematic diagram illustrating a method of fabricating amicrofluidic film by using a master mold of a method of fabricating amicrofluidic film according to another embodiment of the presentinvention;

FIG. 8 is a schematic diagram illustrating a method of disposing amicrofluidic film fabricated by the method of fabricating themicrofluidic film shown in FIG. 2 , on a hard substrate;

FIG. 9 is a block diagram illustrating a method of fabricating amicrofluidic module by attaching a plurality of microfluidic filmsaccording to another embodiment of the present invention; and

FIG. 10 is a schematic diagram illustrating a method of attaching aplurality of microfluidic films so as to fabricate the microfluidicmodule shown in FIG. 9 .

DETAILED DESCRIPTION FOR CARRYING OUT THE INVENTION

Hereinafter, the present invention will be described in detail withreference to the accompanying drawings, in which exemplary embodimentsof the invention are shown.

As illustrated in FIGS. 1 through 6 , a microfluidic film 100 accordingto an embodiment of the present invention includes a base film 110, amicrochannel 120, a through passage 130, and a connection channel 140.The base film 110 is a portion that constitutes the appearance(framework) of the microfluidic film 100. In other words, themicrofluidic film 100 has a structure in which the microchannel 120, thethrough passage 130 and the connection channel 140 are formed on thebase film 110. In the present embodiment, the base film 110 is formed ofresin. In detail, the base film 110 is formed of an Off-stoichiometrythiol-ene polymers (OSTEmer) resin, but any material of the base film110 may be changed.

The microchannel 120 is formed on the base film 110 so that a fluid mayflow through the microchannel 120. The microchannel 120 is formed on thebase film 110 in a longitudinal direction. In the present embodiment,the microchannel 120 is formed in the form of a groove on the base film110. In the present embodiment, the microchannel 120 is a micro-scale ornano-scale channel. However, any size of the microchannel 120 may bechanged.

The through passage 130 is formed to pass through the base film 110. Thethrough passage 130 is formed to fluid-communicate with another basefilm stacked on or below the base film 110. That is, the through passage130 is a passage on which the fluid does not flow only inside the basefilm 110 but flows to another base film outside the base film 110. Inthe present embodiment, the through passage 130 has a hole structure inwhich the through passage 130 is spaced apart from the microchannel 120and passes through the base film 110 from a top surface to a bottomsurface of the base film 110.

The through passage 130 includes a through passage lower hole 131 and athrough passage upper hole 132. The through passage lower hole 131 is aportion that extends from the lower portion of the through passage 130upward by a set length. The through passage upper hole 132 is a portionthat communicates with the upper portion of the through passage lowerhole 131 and extends upward. In this case, in the present embodiment,the through passage upper hole 132 has a greater width than that of thethrough passage lower hole 131. Thus, a step height is formed betweenthe through passage upper hole 132 and the through passage lower hole131. In the present embodiment, the vertical length of the throughpassage upper hole 132 is greater than the vertical length of thethrough passage lower hole 131. In detail, the through passage upperhole 132 has the vertical length of 60 μm, and the through passage lowerhole 131 has the vertical length of 20 μm.

The connection channel 140 allows the microchannel 120 and the throughpassage 130 to communicate with each other. That is, one side of theconnection channel 140 communicates with the microchannel 120, and theother side of the connection channel 140 communicates with the throughpassage 130. In the present embodiment, the connection channel 140 isformed in a horizontal direction crossing the longitudinal direction ina two-dimensional plane of the base film 110. In the present embodiment,a plurality of connection channel 140 are spaced from each other in thelongitudinal direction. Of course, the structure of the connectionchannel 140 may be changed into any structure in which the microchannel120 and the through passage 130 may communicate with each other. In thepresent embodiment, the connection channel 140 is formed in the form ofa groove on the base film 110.

Hereinafter, a method of fabricating the microfluidic film 100 will bedescribed with reference to FIGS. 1 through 6 .

The method of fabricating the microfluidic film 100 includes fabricatinga basic mold B (S100), fabricating a master mold by using the basic moldB (S200), and fabricating a microfluidic film by using the master mold(S300). The fabricating of the basic mold B (S100) is a process offabricating a mold for fabricating the master mold. In the presentembodiment, in the fabricating of the basic mold B (S100), the basicmold B is fabricated using a photolithography process. The basic mold Bincludes a base member formed of a silicon wafer, and the base memberincludes a first base groove having a storage space formed therein, asecond base groove being spaced from the first base groove 130 andhaving a storage space formed therein, and a third base groove throughwhich the first base groove and the second base groove communicate witheach other. In the present embodiment, the first base groove includes afirst base lower groove having a small width of a lower part, and afirst base upper groove that communicates with an upper part of thefirst base lower groove and extends upward.

Although it will be described below, the first base groove has astructure for forming the through passage 130 of the microfluidic film100. The second base groove has a structure for forming the microchannel120 of the microfluidic film 100. The third base groove has a structurefor forming the connection channel 140 of the microfluidic film 100.

The fabricating of the basic mold B (S100) undergoes a first exposureoperation in which a first photoresist is applied onto the silicon waferand a first mask having a first pattern for forming the third basegroove formed thereon is disposed at an upper portion of the firstphotoresist and then light is irradiated onto the first mask. Next, thefabricating of the basic mold B (S100) undergoes a first etchingoperation in which the silicon wafer that has undergone the firstexposure operation is etched by using a developing agent. In the presentembodiment, the first photoresist is a SU-8 photoresist.

Next, a second exposure operation in which, after the first photoresistis removed, a second photoresist is applied onto the silicon wafer, asecond mask having a second pattern for forming the first base lowergroove formed thereon is disposed at an upper portion of the secondphotoresist and then light is irradiated onto the second mask, isperformed. A second etching operation in which the silicon wafer thathas undergone the second exposure operation is etched by using thedeveloping agent, is performed.

Next, a third exposure operation in which, after the second photoresistis removed, a third photoresist is applied onto the silicon wafer, athird mask having a third pattern for forming the first base uppergroove formed thereon and a fourth pattern for forming the second basegroove formed thereon is disposed at an upper portion of the thirdphotoresist and then light is irradiated onto the third mask, isperformed. A third etching operation in which the silicon wafer that hasundergone the third exposure operation is etched by using the developingagent, is performed.

In the silicon wafer according to the present embodiment, the verticallength of the first base upper groove and the vertical length of thesecond base groove are the same. However, the vertical length of thefirst base lower groove is smaller than the vertical length of the firstbase upper groove and the vertical length of the second base groove. Indetail, the vertical length of the first base upper groove and thevertical length of the second base groove are the same, 60 μm, and thevertical length of the first base lower groove is formed to be 20 μm.

The width of the cross-section of the first base lower groove is smallerthan the width of the cross-section of the first base upper groove.Thus, the first base lower groove and the first base upper groove form astep height. This is to help the master mold from being easily separatedfrom the basic mold B when the master mold is fabricated through asoft-lithography process by using the basic mold B.

In fabricating of the master mold (S200), the master mold is fabricatedby using the basic mold B as a template. In the present embodiment, themaster mold formed of polydimethylsiloxane (PDMS) is fabricated by usingthe soft-lithography process. That is, in the present embodiment, PDMSin a liquid state is injected into the basic mold B and then is cured sothat the master mold is fabricated. Any type of polymer for fabricatingthe master mold may be changed.

Because the master mold is complementarily coupled to the basic mold B,a first protrusion is formed in a portion corresponding to the firstbase groove, a second protrusion is formed in a portion corresponding tothe second base groove, and a groove is formed in a portioncorresponding to the third base groove. In particular, the secondprotrusion has a structure in which widths in a vertical direction arethe same. However, a portion of the first protrusion corresponding tothe first base lower groove has a small width, and a portion of thefirst protrusion corresponding to the first base upper grove has a largewidth.

In the present embodiment, the master mold is formed of a materialhaving higher rigidity than that of the basic mold B. Thus, the matermold may be repeatedly used, unlike in the basic mold B. Because, in themethod of fabricating the microfluidic film according to the presentembodiment, cost may be reduced, and mass production is possiblecompared to a case where the microfluidic film is directly fabricated ina way to fabricate the basic mold B by using the silicon wafer.

The fabricating of the microfluidic film (S300) is a process in whichthe microfluidic film 100 including the microchannel 120 and the throughpassage 130 is fabricated by using the master mold as a template. First,the master mold is surface-modified with perfluorooctyltrimethoxysilane(PFOCTS). Next, a glass substrate for forming a template formanufacturing the microfluidic film 100 is prepared together with themaster mold. In this case, the master mold is well attached to the glasssubstrate, and polyvinyl alcohol (PVA) that is soluble in water isspin-coated.

Next, the master mold is attached onto the glass substrate so that theprotruding lower portion of the master mold faces the glass substratecoated with PVA. Next, an OSTEmer resin is loaded between the mastermold and the glass substrate. Subsequently, the OSTEmer resin is curedwith ultraviolet light (UV) 312 nm. In this case, a curing process by UVmakes the OSTEmer resin hard but soft.

Next, the master mold that is reusable is removed. In a state in whichthe master mold is removed, the cured OSTEmer resin is baked at 80° C.By removing the glass substrate and PVA, the microfluidic film 100 isfabricated.

Referring to FIG. 7 , a method of fabricating a microfluidic filmaccording to another embodiment of the present invention is shown. Themethod of fabricating the microfluidic film according to the presentembodiment is different from the method of fabricating the microfluidicfilm shown in FIGS. 2 through 6 that the microfluidic film is fabricatedby using not the master mold of PDMS but the master mold of silicon.That is, after the master mold formed of silicon is fabricated by usingthe basic mold B made in FIG. 3 , the microfluidic film is fabricated byusing the master mold of silicon. Other procedures are similar to thoseof the method of fabricating the microfluidic film shown in FIGS. 2through 6 and thus, a detailed description thereof is omitted.

First, the master mold is surface-modified with PFOCTS. Next, a glasssubstrate for forming a template for fabricating the microfluidic film200 is prepared together with the master mold. In this case, the mastermold is well attached to the glass substrate, and the glass substrate isspin-coated with PVA that is soluble in water. Then, a drop of curingagent is added to the glass substrate coated with PVA.

Next, the curing agent is pressurized with a portion of the master moldhaving an uneven structure (protrusions and grooves) that may becomplementarily coupled to the master mold so that the curing agent isuniformly formed between the glass substrate and the master mold.

Next, the OSTEmer resin is loaded between the master mold and the glasssubstrate. Subsequently, the OSTEmer resin is cured with UV 312 nm. Inthis case, the curing process by UV makes the OSTEmer resin hard butsoft.

Next, the master mold is removed. In a state in which the master mold isremoved, the cured OSTEmer resin is baked at 80° C. Then, by removingthe glass substrate and PVA, the microfluidic film 200 is fabricated.

Referring to FIG. 8 , a process in which the microfluidic film 100fabricated according to FIG. 6 is disposed on a hard substrate, isillustrated. This process is a process in which the microfluidic film100 is attached to the hard substrate to fabricate a two-dimensionalfluidic module. In this case, the hard substrate is formed of a materialhaving higher rigidity than that of the microfluidic film 100.

Referring to FIGS. 9 and 10 , a method of fabricating a microfluidicmodule according to another embodiment of the present invention includespreparing a basic mold (S100′), fabricating a master mold by using abasic mold (S200′), fabricating a first microfluidic film by using themaster mold (S300′), fabricating a second microfluid film by using themaster mold (S400′), and stacking the first microfluidic film and thesecond microfluidic film and attaching the first microfluidic film tothe second microfluidic film (S500′). That is, the microfluidic modulefabricated by the method according to the present embodiment includesthe first microfluidic film and the second microfluidic film.

The preparing of the basic mold (S100′), the fabricating of the mastermold by using the basic mold (S200′), the fabricating of the firstmicrofluidic film by using the master mold (S300′), and the fabricatingof the second microfluid film by using the master mold (S400′) of themethod of fabricating the microfluidic module according to the presentembodiment are similar to those of the method of fabricating themicrofluidic film) shown in FIGS. 2 through 6 . That is, the method offabricating the microfluidic module according to the present embodimentincludes preparing and stacking a plurality of microfluidic filmsfabricated in FIGS. 2 through 5 . Thus, a detailed description of thepreparing of the basic mold (S100′), the fabricating of the master moldby using the basic mold (S200′), the fabricating of the firstmicrofluidic film by using the master mold (S300′), and the fabricatingof the second microfluid film by using the master mold (S400′) isomitted.

Referring to FIG. 10 , FIG. 10 illustrates a process of attaching afirst microfluidic film 1100 to a second microfluidic film 1100′. First,the first microfluidic film 1100 and the second microfluidic film 1100′are prepared. In the present embodiment, the first microfluidic film1100 includes a first base film, a first microchannel, which is formedon the first base film and through which a fluid flows, a first throughpassage configured to pass through the first base film, and a firstconnection channel through which the first microchannel and the firstthrough passage communicate with each other. The second microfluidicfilm 1100′ includes a second base film stacked on the first base film,and a second through passage, which is configured to pass through thesecond base film and communicates with the first through passage.However, the present invention is not limited thereto, and the secondmicrofluidic film 1100′ may further include a second microchannelthrough which the fluid flows on the second base film, and a secondconnection channel allowing the second microchannel and the secondthrough passage to communicate with each other. Also, the first throughpassage may be formed to communicate with not the second through passagebut the second microchannel.

The first microfluid film 1100 according to the present embodiment isfabricated by undergoing a process of curing the OSTEmer resin with UV312 nm in FIG. 6 and removing the master mold that is reusable. Thesecond microfluidic film 1100′ is fabricated through all processes ofFIG. 6 .

Next, the stacking of the first microfluidic film 1100 and the secondmicrofluidic film 1100′ and the attaching of the first microfluidic film1100 to the second microfluidic film 1100′ will be described. First, thefirst microfluidic film 1100 is disposed at a lower portion of a glasssubstrate. A base layer is attached to the second microfluidic film1100′. In the present embodiment, the base layer is ahard-polydimethylsiloxane (H-PDMS) complex. However, any material of thebase layer may be changed. In this case, surface modification is firstperformed. An opposite side of the second microfluidic film 1100′ to aportion in which the base layer is formed, is aligned on the firstmicrofluidic film 1100 and is baked at 80° C. Next, the glass substratedisposed at a lower portion of the first microfluidic film 1100 and PVAare removed to fabricate a microfluidic module. However, the presentinvention is not limited thereto, and the first microfluidic film 1100and the second microfluidic film 1100′ are stacked and attached to eachother through thermal curing.

While the present invention has been particularly shown and describedwith reference to exemplary embodiments thereof, it will be understoodby those of ordinary skill in the art that various changes in form anddetails may be made therein without departing from the spirit and scopeof the present invention as defined by the following claims.

1. A microfluidic film comprising: a base film; a microchannel, which isformed on the base film and through which a fluid flows; and a throughpassage, which is configured to pass through the base film and throughwhich the base film stacked on an upper portion or a lower portion ofthe base film and the fluid communicate with each other.
 2. Themicrofluidic film of claim 1, wherein the microchannel communicates withthe through passage.
 3. The microfluidic film of claim 1, wherein thethrough passage comprises: a through passage lower hole extending from alower portion of the through passage upward; and a through passage upperhole configured to communicate with an upper part of the through passagelower hole, extending upward and having a greater width than a width ofthe through passage lower hole to form a step height with the throughpassage lower hole.
 4. A method of fabricating a microfluidic film, themethod comprising: fabricating a basic mold, the basic mold comprising abase member, a first base groove formed on the base member to extend ina longitudinal direction and having a storage space therein, a secondbase groove formed on the base member, being spaced apart from the firstbase groove and having a storage space therein, and a third base grooveformed between the first base groove and the second base groove so thatthe first base groove and the second base groove communicate with eachother; fabricating a master mold that is repeatedly usable by using thebasic mold as a template; and fabricating a microfluidic film by usingthe master mold as a template, the microfluidic film comprising amicrochannel through which a fluid flows and a through passage forcommunicating with the microfluidic film stacked on an upper portion ora lower portion of the microchannel.
 5. The method of claim 4, wherein,in the fabricating of the basic mold, the base member is a siliconwafer, and the fabricating of the basic mold comprises: a first exposureoperation in which a first photoresist is applied onto the siliconwafer, a first mask having a first pattern for forming the third basegroove therein is disposed at an upper portion of the first photoresistand light is irradiated to the first mask; and a first etching exposureoperation in which the silicon wafer that has undergone the firstexposure operation is etched by using a developing agent.
 6. The methodof claim 5, wherein the first base groove comprises a first base lowergroove having a small width of a lower part and a first base uppergroove communicating with an upper part of the first base lower grooveand extending upward, and the method further comprises: a secondexposure operation in which, after the first photoresist is removed, asecond photoresist is applied onto the silicon wafer, a second maskhaving a second pattern for forming the first base lower groove thereinis disposed at an upper portion of the second photoresist and light isirradiated onto the second mask; and a second etching operation in whichthe silicon wafer that has undergone the second exposure operation isetched by using a developing agent.
 7. The method of claim 6, furthercomprising: a third exposure operation in which, after the secondphotoresist is removed, a third photoresist is applied onto the siliconwafer, a third mask having a third pattern for forming the first baseupper groove and a fourth pattern for forming the second base groovetherein is disposed at an upper portion of the third photoresist andlight is irradiated onto the third mask; and a third etching operationin which the silicon wafer that has undergone the third exposureoperation is etched by using a developing agent.
 8. The method of claim7, wherein, in the silicon wafer, a vertical length of the first baseupper groove and a vertical length of the second base groove are thesame.
 9. The method of claim 8, wherein a width of a cross-section ofthe first base lower groove is smaller than a width of the cross-sectionof the first base upper groove so that the first base lower groove andthe first base upper groove form a step height.
 10. The method of claim9, wherein a vertical length of the first base upper groove is greaterthan a vertical length of the first base lower groove.
 11. The method ofclaim 10, wherein, in the fabricating of the master mold, polymer isinjected into the basic mold and is cured to fabricate the master mold.12. The method of claim 11, wherein the polymer comprisesPolydimethylsiloxane (PDMS).
 13. The method of claim 4, wherein thefabricating of the microfluidic film comprises: modifying a surface ofthe master mold; preparing a glass substrate for forming a template forfabricating the microfluidic film together with the master mold;attaching a portion of the master mold having an uneven structure thatis complementarily coupled to the basic mold, onto the glass substrate;loading a resin for forming the microfluidic film between the mastermold and the glass substrate and curing the resin; separating the mastermold from the cured resin; and separating the glass substrate from thecured resin.
 14. The method of claim 13, wherein the preparing of theglass substrate further comprises coating the glass substrate withpolyvinyl alcohol (PVA) so that the master mold is well attached ontothe glass substrate.
 15. The method of claim 13, further comprising,between the preparing of the glass substrate and the attaching of themaster mold onto the glass substrate: disposing a curing agent on theglass substrate; and pressurizing the curing agent with a portion of themaster mold having an uneven structure that is complementarily coupledto the basic mold so that the curing agent is uniformly formed betweenthe glass substrate and the master mold.
 16. The method of claim 4,wherein, in the fabricating of the master mold, the master mold ofpolydimethylsiloxane (PDMS) is fabricated by using a soft-lithographyprocess.